Recently, there have been made great technological advances in disk recording/reproducing apparatus (hereinafter referred to as “disk drives”) for recording and/or reproducing data on a disk-shaped recording medium such as a hard disk or an optical disk (hereinafter referred to as “disks”) and their use is expanding not only in conventional computers but also in many other fields. There are increasing demands for such disk drives to have high recording density and, in addition, to be small in size, consume little power, have good shock resistance, and be mountable onto portable equipment.
FIG. 14 is a perspective view schematically showing a disk drive. In FIG. 14, a disk 2 is supported on a main spindle 1 so as to be rotatively driven by a driving means 3. As driving means 3, a spindle motor for example is used. A head slider 4 having a head (not shown) for performing a record/reproduce operation (i.e., for performing a recording and/or a reproducing operation) is supported on a suspension 5 and the suspension 5 is fixed to an actuator arm 6. Actuator arm 6 is attached to actuator shaft 7 for rotation.
A positioning means 8, for example a voice coil motor, allows actuator arm 6 to swing so that head slider 4 is shifted to a predetermined track position of disk 2. A housing 9 serves to keep the above described members in predetermined relative positions and, by being covered with a lid (not shown) serves also to protect the above-mentioned components and other components within the housing.
While a record/reproduce operation is performed in the disk drive having the described structure, the following three forces are applied to the head slider 4 and a balance among these three forces allows head slider 4 to fly while maintaining a designed flying height. The first of the forces is the load exerted by suspension 5 such that head slider 4 is urged in the direction of the disk. The second is a force resulting from a flow of viscous fluid such as air accompanying the rotation of the disk and this is a positive pressure acting to urge the head slider 4 to fly above disk 2. The third is a force similarly resulting from a flow of viscous fluid such as air accompanying the rotation of the disk but this is a negative pressure acting to urge the head slider 4 toward the disk 2. While head slider 4 is flying at a predetermined flying height by virtue of the balance among the three forces, positioning means 8 is driven so that head slider 4 is shifted to a predetermined track position and a record/reproduce operation is performed by the head (not shown).
With the increase in the recording capacity per unit area of disks, disk drives of smaller size and smaller thickness have come to be realized and mounted on portable equipment such as notebook-size personal computers. For example, disks have become as small as 3.5 in., 2.5 in., or as small as 1.3 in., in diameter. As the disk diameter is decreased, the number of revolutions of the disk 2 is accordingly increased. Thus, the rotation speeds of these smaller diameter disks are increased to 4500 rpm, 5400 rpm, and 7200 rpm, respectively. Thus, when the diameter of disk 2 is decreased, it has conventionally been required to increase the number of revolutions of disk 2 in order to maintain the relative speed between disk 2 and head slider 4 at required levels.
In order to realize a still smaller disk drive and to have it mounted on portable equipment represented by mobile telephones, there also arises a very important problem of reducing the power consumption. More specifically, though smaller diameter disks are required in order for disk drives to be mounted on portable equipment, it is a problem to increase the number of revolutions because doing so incurs an increase in power consumption. Also, it is required to maintain a stable flying height of the disk even if the relative speed between the head slider and the disk becomes low when such a smaller sized disk is used. It is further required, even when external shock is exerted on the head slider, that wear and tear or damage to the head slider or the disk due to collision or contact of the head slider with the disk be prevented.
A structure of a head slider capable of flying above the disk surface even if the relative speed between the head slider and the disk is low is disclosed in Japanese Patent Unexamined Publication No. 2001-229518. In the disclosed head slider, there are formed grooves of different depths in the surface of the head slider opposite the disk, whereby stepped portions having at least two steps are formed, and the depth of the shallowest groove of the grooves forming such stepped portions is set to 250 nm or below. It is stated therein that a stable flying height can be maintained by the use of this head slider even if the relative speed between the head slider and the disk is low.
Although it is stated in the disclosure cited that the head slider is kept at a stable flying state so as not to cause a collision with the disk when the relative speed is low, it is not stated that the head slider, while flying with a low relative speed, is prevented from causing damage on the head slider or the disk when the head slider is subjected to a shock force.